Signaling of Sequence Generator Initialization Parameters for Uplink Reference Signal Generation

ABSTRACT

A base station initializes pseudo-random sequence generators on which wireless devices base generation of uplink reference signals. The base station determines a first sequence from a first subset of possible initialization sequences for a sequence generator of a first device, and determines a second sequence from a second subset of possible initialization sequences for a sequence generator of a second device. The range of this second subset spans at least the range of the first subset. The base station further encodes the first sequence as a first set of two or more parameters, and encodes the second sequence as a second set of one or more parameters. This second set includes at least one parameter not included in the first set, and comprises fewer bits than the first set. The base station initializes the sequence generators by transmitting the first and second sets of parameters to the devices.

RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/468,855, filed on May 10, 2012, which claims priority to U.S.Provisional Patent Application Ser. No. 61/616,866, filed Mar. 28, 2012,the entire contents of both are incorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to initialization ofpseudo-random sequence generators on which wireless devices basegeneration of uplink reference signals, and more particularly relates toadvantageous techniques for encoding and signaling parameters for suchinitialization.

BACKGROUND

A wireless device (also referred to as a user equipment, UE) transmitsone or more uplink reference signals in a wireless communication systemfor any number of reasons, such as to permit the receiving base stationto estimate the wireless channel. The wireless device typicallygenerates a reference signal using one or more pseudo-random sequencegenerators. Accordingly, initialization of the sequence generator(s)with particular initialization sequence(s) dictates the uplink referencesignal that the device transmits. The base station governs theinitialization of the device's sequence generator(s) in this regard,meaning that signaling an initialization sequence to a wireless devicepresents challenges in terms of signaling overhead.

Consider, for instance, Long Term Evolution (LTE) networks. LTE networksare designed with the aim of enabling optional CoMP (Coordinatedmultipoint processing) techniques, where different sectors and/or cellsoperate in a coordinated way in terms of, e.g., scheduling and/orprocessing. An example is uplink (UL) CoMP where the signal originatingfrom a single UE is typically received at multiple reception points andjointly processed in order to improve the link quality. UL jointprocessing (also referred to as UL CoMP) allows transformation of whatis regarded as inter-cell interference in a traditional deployment intoa useful signal. Therefore, LTE networks taking advantage of UL CoMP maybe deployed with a smaller cell size compared to traditionaldeployments, in order to fully take advantage of the CoMP gains.

The LTE UL is designed assuming coherent processing, i.e., the receiveris assumed to be able to estimate the radio channel from thetransmitting UE and to take advantage of such information in thedetection phase. Therefore, each transmitting UE sends a referencesignal (RS) associated with each UL data or control channel (e.g., PUSCHand PUCCH). 3GPP TS 36.211 V10.4.0 (2011-12), “Technical SpecificationGroup Radio Access Network; Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation (Release 10).” In case ofPUSCH, one demodulation reference signal (DMRS) per slot is transmittedon the same bandwidth as the uplink data channel. In case of PUCCH,multiple PUCCH-RSs are transmitted and time multiplexed by the UE withineach subframe, spanning the PUCCH bandwidth assigned to the UE.

Additional RSs possibly transmitted by UEs consist of sounding referencesignals (SRS). These reference signals are transmitted by a UE atpredetermined time instances and over a predetermined bandwidth, inorder to enable estimation of the UL channel properties at the networkside.

RSs from different UEs within the same cell potentially interfere witheach other and, assuming synchronized networks, even with RS originatedby UEs in neighboring cells. In order to limit the level of interferencebetween RSs, different techniques have been introduced in different LTEreleases in order to allow orthogonal or semi-orthogonal RSs. The designprinciple of LTE assumes orthogonal RS within each cell andsemi-orthogonal RS among different cells (even though orthogonal RSs canbe achieved for aggregates of cells by so called “sequence planning”).However, orthogonality of DMRS transmitted by UEs belonging to differentcell is currently under discussion in Rel-11 LTE standardization. Afamily of techniques for inter-cell DMRS orthogonality has beendiscussed. Some of these techniques rely on the possibility ofcoordinating the base-sequence index (BSI) employed for RS generation bydifferent UEs in different cells, as described more fully later.

Another application in the UL of LTE is multi-user, multiple-inputmultiple-output (MU-MIMO), where data transmissions on PUSCH frommultiple UEs are coscheduled on at least partly overlapping bandwidth inthe same subframe, within the same cell. The UEs are separated at thereceiver side by exploiting multiantenna processing. In order to allowthe receiver to resolve the signals from the coscheduled UEs, it isbeneficial to assign the DMRS in an orthogonal fashion for such UEs.This may be achieved by assigning different orthogonal cover codes(OCCs) to the DMRS of the coscheduled UEs. If the coscheduled bandwidthsare fully overlapping, cyclic shift (CS) separation of the DMRS for thedifferent UEs may also be exploited.

Each DMRS is characterized by a group-index and a sequence-index, whichdefine the so called base-sequence index (BSI). BSIs are assigned in acell-specific fashion in Rel-8/9/10 and they are a function of thecell-ID, where a cell-ID characterizes a cell in LTE and affects severalcell-specific algorithms and procedures. Different base sequences aresemi-orthogonal, which implies that some inter-sequence interference ispresent in the general case. The DMRS for a given UE is only transmittedon the same bandwidth of PUSCH and the base sequence is correspondinglygenerated so that the RS signal is a function of the PUSCH bandwidth.For each subframe, 2 RSs are transmitted, one per slot. In Rel-11 it islikely that UE-specific assignment of BSIs will be introduced.

Orthogonal DMRS can be achieved by use of cyclic shift (CS) in Rel-8/9or by CS in conjunction with orthogonal OCC in Rel-10. CS is a method toachieve orthogonality based on cyclic time shifts, under certainpropagation conditions, among RS generated from the same base sequence.Only 8 different CS values can be dynamically indexed in Rel-8/9/10,even though in practice less than 8 orthogonal DMRS can be achieveddepending on channel propagation properties (without considering OCC inthis example). Even though CS is effective in multiplexing DMRSsassigned to fully overlapping bandwidths, orthogonality is lost when thebandwidths differ and/or when the interfering UE employs another basesequence.

In order to increase interference randomization between different UEs(e.g., at different cells), a pseudo-random offset to the CS values isapplied (CS hopping, CSH). The randomization pattern is cell-specific inRel-8/9/10. A different CS offset is in general applied in each slot andit is known at both UE and eNB sides, so that it can be compensated atthe receiver side during channel estimation. A CSH is generatedaccording to a sequence initialization parameter c_(init) having 31bits.

OCC is a multiplexing technique based on orthogonal time domain codes,operating on the 2 RS provided for each UL subframe. The OCC code [1 −1]is able to suppress an interfering DMRS as long as its contributionafter the matched filter at the receiver is identical on both DMRSs ofthe same subframe. Similarly, the OCC code [1 1] is able to suppress aninterfering DMRS as long as its contribution after the eNB matchedfilter has opposite sign respectively on the two RSs of the samesubframe. It is straightforward to assume that CS and OCC will besupported also by Rel-11 UEs.

While base-sequences are assigned in a semi-static fashion, CS and OCCare dynamically assigned as part of the scheduling grant for each ULPUSCH transmission. Even though joint processing techniques may beapplied for PUSCH, channel estimates based on DMRS are typicallyperformed in an independent fashion at each reception point, even incase of UL CoMP. Therefore, it is crucial to keep the interference levelat an acceptably low level, especially for RSs.

In case of SRS, the RSs are also generated according to a BSI (which maydiffer from the DMRS BSI for some UEs). Different SRS may be multiplexedby use of CS and COMBs. A COMB indicates a specific interleaved mappingof the RS to a subset of subcarriers. SRS assigned to different COMBS(i.e., non overlapping sets of subcarriers) are thus ideally orthogonal.

In case of PUCCH-RS, one or more RS per slot are generated, depending onthe PUCCH format and other parameters. PUCCH-RS for different UEs areseparated by use of CS and OCC, which spans over each slot. AlsoPUCCH-RS are generated according to a BSI that may in general differfrom the DMRS BSI.

One of the improvements being discussed in LTE Rel-11 consists of thepossibility of configuring the parameters for BSI and CSH initializationin a UE specific fashion, either semi-statically or dynamically, e.g.,by signaling in the scheduling grants. Such configurability allowsadditional RS allocations options enabling, e.g., inter-cellorthogonality between UEs. R1-121028—“Details about UL DMRSconfiguration and signaling.” In order to achieve orthogonality by OCC,it is necessary to configure the paired UEs with the same CSH pattern.Problematically, however, the CSH initialization c_(init) is a 31 bitparameter, requiring significant overhead for being signaled.

SUMMARY

One or more embodiments herein advantageously reduce control signalingbetween a base station and a wireless device in a wireless communicationsystem, as compared to known control signaling approaches. Theembodiments in particular reduce the control signaling for initializingpseudo-random sequence generators on which wireless devices basegeneration of uplink reference signals.

More particularly, one or more embodiments include a base stationconfigured to initialize pseudo-random sequence generators on whichwireless devices base generation of uplink reference signals. The basestation is configured to determine a first sequence from a first subsetof possible initialization sequences for a pseudo-random sequencegenerator of a first wireless device, and to determine a second sequencefrom a second subset of possible initialization sequences for apseudo-random sequence generator of a second wireless device. The rangeof this second subset spans at least the range of the first subset.

The base station further encodes the first sequence as a first set oftwo or more parameters, and encodes the second sequence as a second setof one or more parameters. This second set of parameters includes atleast one parameter not included in the first set of parameters, andcomprises fewer bits than the first set. Having performed this encoding,processing the base station initializes the sequence generators of thefirst and second devices with the first and second sequences bytransmitting the first and second sets of parameters to the first andsecond devices. Upon receiving the sets of parameters, the devicesdecode the sequences according to one or more rules that define thesequences as a function of those sets of parameters and then generatethe uplink reference signals based on those sequences.

In at least some embodiments, the base station encodes the secondsequence as a single parameter. In one embodiment, for example, thissingle parameter comprises a defined number of least significant bitsfrom the second sequence corresponding to the range of the secondsubset. In another embodiment, by contrast, the second sequence isencoded based on a defined one-to-one mapping of possible initializationsequences within the second subset to possible values for the singleparameter, wherein the range of the single parameter is smaller than therange of the second subset.

In other embodiments, the base station encodes the second sequence as alinear combination of two parameters. In this case, a first one of thetwo parameters encodes a defined number of least significant bits fromthe second sequence, and a second one of the two parameters encodes adefined number of more significant bits from the second sequence (notincluding one or more most significant bits from the second sequence).

In any case, the second sequence is encoded as a second set ofparameters that comprises only 9 or 10 bits in some embodiments, whichis significantly fewer bits than the 31 bits required to signal thesecond sequence itself in those embodiments. The embodiments therebyprove to reduce control signaling associated with the signaling of thesecond sequence.

In one or more embodiments where the initialization sequences correspondto cyclic shift hopping patterns for the devices, the firstinitialization sequence comprises a cell-specific sequence and thesecond initialization sequence comprises a device-specific sequence. Thebase station initializes the sequence generators in this way in order tomaintain backwards compatibility with respect to the first device, whileachieving inter-cell orthogonality for the second device with respect toa third wireless device in a different cell. Where the embodimentsemploy LTE, for example, the first and third devices comprise legacydevices that are configured for LTE Rel-8/9/10, and the second devicecomprises a newer device that is configured for LTE Rel-11.

In this case, the base station determines the second sequence for thesecond device by selecting from the second subset the initializationsequence that matches the initialization sequence for a pseudo-randomsequence generator of the third device. The base station is able to dothis because the range of the second subset spans at least the range ofthe subset of possible initialization sequences for the third device;that is, the initialization sequence for the second device is able totake on values that are possible for the third device. With theinitialization sequences (and therefore the cyclic shift hoppingpatterns) for the second and third devices the same, the base station isable to achieve inter-cell orthogonality for these paired devicesthrough use of different orthogonal cover codes (OCCs) for the devices.Notably, therefore, by configuring the initialization sequences in thisway, the base station is able to arbitrarily pair a newer device in onecell with any legacy device in a different cell for achieving inter-cellorthogonality between those devices' uplink reference signals.

Of course, the present invention is not limited to the above featuresand advantages. Indeed, those skilled in the art will recognizeadditional features and advantages upon reading the following detaileddescription, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication system with a basestation and a wireless device configured according to one or moreembodiments herein for sequence generator initialization.

FIG. 2 is a logic flow diagram of processing performed by a base stationfor initializing pseudo-random sequence generators according to one ormore embodiments herein.

FIG. 3 illustrates an example of a base station's encoding ofinitialization sequences for different wireless devices according to oneor more embodiments.

FIG. 4 is a logic flow diagram of processing performed by a base stationfor initializing pseudo-random sequence generators according to one ormore other embodiments herein.

FIG. 5 is a table that illustrates an example one-to-one mapping betweenthe decimal representation of possible initialization sequences andpossible values for a single parameter according to one or moreembodiments.

FIGS. 6A-6B are tables that illustrate different examples of jointencoding according to one or more embodiments.

FIG. 7 is a logic flow diagram of processing performed by a wirelessdevice for initializing a pseudo-random sequence generator according toone or more embodiments herein.

FIG. 8 is a table that illustrates an example one-to-one mapping betweenthe decimal representation of possible initialization sequences andpossible values for a set of parameters according to one or moreembodiments.

FIG. 9 is a block diagram that illustrates a wireless device configuredto initialize a pseudo-random sequence generator according to one ormore embodiments herein.

FIG. 10 is a block diagram that illustrates a base station configured toinitialize pseudo-random sequence generators according to one or moreembodiments herein.

DETAILED DESCRIPTION

FIG. 1 depicts a wireless communication system 10 according to one ormore embodiments. The system 10 includes a radio access network (RAN)that comprises a plurality of geographically distributed base stations12-1, 12-2, . . . 12-N. The base stations 12-1, 12-2, . . . 12-N(referred to collectively as base stations 12) provide wirelesscommunication coverage to wireless devices 16-1, 16-2, . . . 16-M withinrespective areas referred to as cells 14-1, 14-2, . . . 14-N. Throughthe base stations 12, the wireless devices 16 access a core network 18,which in turn connects the devices 16 to one or more external networks20, e.g., the Internet.

The wireless devices 16 transmit respective uplink reference signals 22to the base stations 12. The base stations 12 employ the uplinkreference signals for various reasons, such as to estimate therespective wireless channels between the base stations 12 and thedevices 16. The uplink reference signals may comprise, for instance,demodulation reference signals (DMRS) that the base stations 12 use todemodulate uplink data and/or control signals, sounding referencesignals (SRSs), or the like. Regardless, the devices 16 employpseudo-random sequence generators in order to generate these uplinkreference signals 22. Any given device 16-m may, for example, employ twosequence generators to generate two maximal-length sequences and thenmodulo-2 add those sequences to form a Gold sequence on which an uplinkreference signal 22 for the device 16 is based. This Gold sequence insome embodiments, for instance, dictates a cyclic shift hopping (CSH)pattern that the device 16 applies to a cyclic shift and then appliesthe resulting cyclic shift to a base sequence in order to generate theuplink reference signal 22.

A base station 12-n governs the uplink reference signal 22-m that anygiven device 16-m transmits by, among other things, governinginitialization of one or more of the device's pseudo-random sequencegenerators. In this regard, a base station 12-n initializes a device'ssequence generator by informing the device of an initialization sequenceto which the generator is to be initialized, such as an initializationsequence represented in decimal form c_(init) in LTE embodiments. Insome embodiments, a base station 12-n initializes different devices'sequence generators with different (i.e., device-specific)initialization sequences, e.g., to distinguish the devices' uplinkreference signals 22 on that basis. In other embodiments, though, a basestation 12-n initializes different devices' sequence generators with acommon (e.g., cell-specific) initialization sequence, whiledistinguishing the devices' uplink reference signals 22 on other bases.In still other embodiments, the a base station 12-n initializes somedevices' sequence generators with device-specific sequences, and otherdevices' sequence generators with cell-specific sequences. Regardless, abase station 12-n herein advantageously encodes initialization sequencesfor at least some devices 16 in different ways, so as to reduce theamount of control signaling required for indicating those sequences ascompared to known approaches.

FIG. 2 illustrates base station processing according to one or moreembodiments in this regard, with reference to base station 12-1,wireless device 16-1, and wireless device 16-2 as an example. Wirelessdevices 16-1 and 16-2 need not be present within the base station's cell14-1 at the same time in order for the base station 12-1 to perform theprocessing illustrated in FIG. 2. Indeed, as described below, the basestation 12-1 determines, encodes, and signals an initialization sequencefor device 16-1 independently from its determination, encoding, andsignaling of an initialization sequence for device 16-2. Such remainsthe case regardless of whether or not the same initialization sequenceis determined for the devices 16-1, 16-2 (e.g., where the sequence iscell-specific) and regardless of whether or not the initializationsequences for the devices 16-1, 16-2 are encoded using at least onecommon parameter. This independent processing means that the basestation 12-1 may be configured in at least some embodiments todetermine, encode, and signal an initialization sequence for device 16-1at a different time than its determination, encoding, and signaling ofan initialization sequence for device 16-2.

With this in mind, processing implemented by base station 12-1 in FIG. 2includes determining a first sequence from a first subset of possibleinitialization sequences for a pseudo-random sequence generator of afirst wireless device 16-1 (Block 100). Processing further includesdetermining a second sequence from a second subset of possibleinitialization sequences for a pseudo-random sequence generator of asecond wireless device 16-2 (Block 110). The range of this second subsetof possible sequences spans at least the range of the first subset ofpossible sequences. Determining a sequence in this way may involvecomputing the sequence, obtaining the sequence from memory, or acquiringthe sequence in some other fashion, and may comprise determining acell-specific sequence employed by another cell (e.g., cell 14-2).

Regardless of how these sequences are determined, processing at basestation 12-1 also entails encoding the first sequence as a first set oftwo or more parameters (Block 120), and encoding the second sequence asa second set of one or more parameters (Block 130). This second set ofparameters includes at least one parameter not included in the first setof parameters, and comprises fewer bits than the first set. That is, theinitialization sequence for the second device 16-2 is encoded with fewerbits than the initialization sequence for the first device 16-1, eventhough the range of possible initialization sequences to be signaled tothe second device 16-2 (i.e., the range of the second subset) spans atleast the range of possible initialization sequences to be signaled tothe first device 16-1 (i.e., the range of the first subset). Havingperformed this encoding, processing at the base station 12-1 finallyincludes initializing the sequence generators of the first and seconddevices 16-1, 16-2 with the first and second sequences by transmittingthe first and second sets of parameters to the first and second devices16-1, 16-2 (Block 140). As mentioned above, such initialization andtransmission may be performed independently and at different times forthe different devices 16-1, 16-2.

Upon receiving the first set of parameters, the first device 16-1decodes the first sequence according to one or more rules that definethe sequence as a function of the first set of parameters and thengenerates the uplink reference signal with the device's sequencegenerator initialized to that sequence. When the first device 16-1transmits the uplink reference signal to the base station 12-1, the basestation 12-1 employs the first set of parameters in order to estimatethe wireless communication channel to the first device 16-1 based on theuplink reference signal. Likewise, upon receiving the second set ofparameters, the second device 16-2 decodes the second sequence accordingto one or more rules that define the sequence as a function of thesecond set of parameters and then generates the uplink reference signalwith the device's sequence generator initialized to that sequence. Whenthe second device 16-2 transmits the uplink reference signal to the basestation 12-1, the base station 12-1 employs the second set of parametersin order to estimate the wireless communication channel to the seconddevice 16-2 based on the uplink reference signal.

FIG. 3 illustrates a pictorial representation of one simple example ofthe base station processing. (This simple example, however, isnon-limiting in terms of the number of bits used and the position of thesubsets). As shown in FIG. 3, the sequence generator of a first wirelessdevice 16-1 comprises 31 bits (labeled 0 through 30 from the leastsignificant bit). Thus, a full set 24-1 of possible initializationsequences for the sequence generator of the first device 16-1 at leastnominally includes sequence ‘000 . . . 000’ to sequence ‘111 . . . 111’(i.e., a decimal range from 2⁰ to 2³⁰). The same can be said for a fullset 24-2 of possible initialization sequences for the sequence generatorof the second device 16-2 in this example.

Despite the nominal possibilities provided by the full sets 24-1, 24-2of initialization sequences, though, the base station 12-1 excludes someof those possibilities from consideration in determining the actualinitialization sequences for the devices 16-1, 16-2, so as to therebyartificially limit the initialization sequences to be signaled.Specifically, the base station 12-1 determines a first sequence 26-1 forthe first device 16-1 from only a subset 28-1 of possible initializationsequences, and determines a second sequences 26-2 for the second device16-2 from only a subset 28-2 of possible initialization sequences. Asshown, the possible sequences within these subsets 28-1, 28-2 stillcomprise 31 bits; that is the number of bits corresponding to the rangeof the full sets 24-1, 24-2 of possible sequences. However, thesequences within the subsets 28-1, 28-2 have 0's for the 21 mostsignificant bits, meaning that the ranges 30-1, 30-2 of the subsets28-1, 28-2 are represented by only the 10 least significant bits. Inthis case, the range 30-2 of the second subset 28-2 spans the same rangeas the range 30-1 of the first subset 28-1. In general, though, therange 30-2 of the second subset 28-2 may span a greater range than therange 30-1 of the first subset 28-1 (e.g., decimal 1023 vs. 541), evenif the two subsets 28-1, 28-2 are represented by the same number ofbits.

Regardless, the base station 12-1 encodes the first sequence 26-1 forthe first device 16-1 differently than the way it encodes the secondsequence 26-2 for the second device 16-2. In some embodiments, forinstance, the first and second devices 16-1, 16-2 are different types ormodels of devices and are therefore configured to decode the sequences26-1, 26-2 in different ways. The first device 16-1 in one examplecomprises a legacy device that is configured for LTE Rel-8/9/10 and thesecond device 16-2 comprises a newer device that is configured for LTERel-11. As explained in greater detail below, because the range 30-2 ofthe second subset 28-2 spans at least as great as range as the range30-1 of the first subset 28-1, the base station 12-1 is advantageouslyable in this case to allocate the same initialization sequence to alegacy device and a new device, but to signal the initializationsequence to the new device in a more efficient manner.

In any event, the base station 12-1 encodes the first sequence 26-1 as afirst set 32-1 of two or more parameters, and encodes the secondsequence 26-2 as a second set 32-2 of one or more parameters. Theencoding of the second sequence 26-2 is optimized with respect to theencoding of the first sequence 26-1 at least in the sense that thesecond set 32-2 comprises fewer bits than the first set 32-1, eventhough the second set 32-2 is capable of representing at least as greatof range of possible initialization sequences as the first set 32-1.These sets 32-1, 32-2 of parameters are then signaled to the wirelessdevices 16-1, 16-2 rather than the actual initialization sequences 26-1,26-2. Each set 32-1, 32-2 of parameters requires fewer bits to signalthan that required to signal the 31 bit sequences 26-1, 26-2 themselves,meaning that the encoding advantageously reduces the amount of controlsignaling required to indicate the sequences 26-1, 26-2 to the devices16-1, 16-2.

In some embodiments, the second sequence 26-2 is encoded as a singleparameter z, while the first sequence 26-1 is encoded as two or moreparameters. That is, the second set 32-2 has only one parameter, namelyz, even though the first set 32-1 has more than one parameter.

FIG. 4 depicts processing at the base station 12-1 with particularregard to this single parameter encoding. As shown in FIG. 4, processingat the base station 12-1 entails determining a sequence 26-2 from asubset 28-2 of possible initialization sequences for the sequencegenerator of a wireless device 16-2 (Block 200). Processing thenincludes encoding the determined sequence 26-2 as a single parameter z(Block 210). Different values for this single parameter z representdifferent possible initialization sequences within the subset 28-2.Processing finally includes initializing the sequence generator for thewireless device 16-2 with the determined sequence 26-2 by transmittingthe single parameter z to the device 16-2 (Block 220).

In at least one embodiment, the single parameter z comprises a definednumber of least significant bits from the second sequence 26-2, wherethe defined number corresponds to the range 30-2 of the second subset28-2. In the example of FIG. 3, this single parameter z would thereforecomprise the 10 least significant bits of the second sequence 26-2.Regardless, in this embodiment, the base station 12-1's encoding entailstruncating a defined number of most significant bits of the secondsequence 26-2 (e.g., the 21 most significant bits, namely bits 10 to30), since those bits are 0's in all possible sequences within thesecond subset 28-2. The second device 16-2 will perform a decoding thatpads the single parameter z with 0's, e.g., by pre-pending 0's to thesingle parameter z. Those skilled in the art will appreciate, however,that padding may be performed by the second device 16-2 in differentways in other embodiments. For example, in some embodiments the seconddevice 16-2 pads the single parameter z by appending 0's to thatparameter.

In at least one other embodiment, the second sequence 26-2 is encodedbased on a defined one-to-one mapping of possible initializationsequences within the second subset 30-2 to possible values for thesingle parameter z. Notably, though, the range of the single parameter zis smaller than the range 30-2 of the second subset 28-2. The definedmapping in this sense effectively compresses the range 30-2 of thesecond subset 28-2 into the single parameter z so as to signal thesecond sequence 26-2 with fewer bits.

FIG. 5 illustrates an example defined mapping in the context of an LTEembodiment where the second sequence 26-2 selected from the secondsubset 28-2 is represented as c_(init), which is a decimalrepresentation of the second sequence 26-2. As shown in FIG. 4, thesubset 28-2 of possible initialization sequences c_(init) is sparse inthe sense that it does not include all initialization sequences withinthe subset's range 30-2. For example, the subset 28-2 does not includec_(init) values of 30, 31, 62, 63, 94, 95, and so forth, even though thesubset's range 30-2 spans from c_(init) values of 0 to 541. The definedmapping maps those possible initialization sequences c_(init) within thesubset 28-2 to possible values for the single parameter z (here, shownas a decimal representation), so that z is not sparse. According to themapping, the initialization sequences c_(init)=32 is encoded as z=30,c_(init)=33 is encoded as z=31, c_(init)=64 is encoded as z=60,c_(init)=65 is encoded as z=61, and so forth. Due to the nature of thismapping, the {0,541} range 30-2 of the second subset 28-2 of possibleinitialization sequences c_(init) is compressed into a {0,509} range ofthe single parameter z. Notably, therefore, signaling of the singleparameter z requires 9 bits, which is 1 fewer bit to signal than the 10bits that would be required to signal the parameter z as described abovewithout this compression.

FIG. 5 of course illustrates the defined mapping as being a look-uptable that is obtained by the base station 12-1 for encoding. The basestation 12-1 in some embodiments obtains the table from memory, while inother embodiments the base station 12-1 obtains the table by generatingit on an as needed basis, according to a predefined formula. In eithercase, the base station 12-1 selects the second sequence 26-2 c_(init)from the second subset 28-2 and then determines the parameter z thatcorresponds to the selected sequence c_(init) in the look-up table.

In other embodiments, the mapping is embodied in ways other than alook-up table. In one embodiment, for example, the defined mappingexists as an algorithm or formula used by the base station 12-1 forencoding. Specifically, the base station 12-1 encodes the selectedinitialization sequence c_(init) as the single parameter

${z = {c_{init} - {2\lfloor \frac{c_{init}}{32} \rfloor}}},$

where └x┘ denotes a floor function that rounds x to the nearest integerless than or equal to x.

Furthermore, although FIG. 5 illustrates the single parameter z as if ithas the minimum range needed for compressing the range of the secondsubset 28-2 of possible initialization sequences c_(init), this need notbe the case. Consider, for example, embodiments where the secondsequence 26-2 c_(init) corresponds to a CSH that the device 16-2 appliesto a cyclic shift for generating the uplink reference signal 22-2. Inone or more embodiments in this case, the base station 12-1 jointlyencodes the second sequence 26-2 c_(init) and an indication of whetheror not CSH is enabled as the second set 32-2 of one or more parameters.Thus, where the second set 32-2 of parameters just includes the singleparameter z, the range of z is extended in order to indicate whether ornot CSH is enabled.

FIGS. 6A-6B illustrate two different examples of this. In both examples,the base station 12-1 performs joint encoding such that the singleparameter z not only indicates the second sequence 26-2 c_(init) asdescribed above, but also indicates a flag called CSH_ENABLE. IfCSH_ENABLE=1, CSH is enabled. If CSH_ENABEL=0, CSH is not enabled.

According to the joint encoding in FIG. 6A, the base station 12-1performs joint encoding such that the single parameter z indicates thatCSH_ENABLE=1 if the parameter z has a decimal value between 0 and 509.These possible values of z similarly map to possible initializationsequences c_(init), as shown in FIG. 5, meaning that the joint encodingalso indicates the initialization sequence c_(init) to be used whenCSH_ENABLE=1. By contrast, if the parameter z has any other decimalvalue, the parameter z indicates that CSH_ENABLE=0. With CSH disabled inthis case, the initialization sequences c_(init) is not defined, or atleast is not relevant.

Although FIG. 6A contemplates that one or more values of the singleparameter z (jointly or individually) indicate that CSH is disabled,FIG. 6B more specifically shows a single value (i.e., z=511) asindicating that CSH is disabled. Indicating CSH_ENABLE with only asingle value of the parameter z proves simpler in practice, and alsoallows for the signaling of additional information other than theinitialization sequence c_(init) and CSH_ENABLE. Of course, embodimentsthat only utilize 512 values for the parameter z prove advantageous forsignaling z with only 9 bits, rather than 10 bits for embodiments thatutilize more than 512 values for z.

Regardless of whether or not such joint encoding is employed, though,the second wireless device 16-2 herein is configured to receive thesingle parameter z from the base station 12-1 and to initialize apseudo-random sequence generator on which to base uplink referencesignal generation according to that single parameter z. FIG. 7illustrates processing that the device 16-2 performs in this regard.

As shown in FIG. 7, processing at the device 16-2 entails selectivelyderiving one of the second initialization sequences 26-2 within thesecond subset 28-2 of possible initialization sequences for the sequencegenerator, according to one or more rules that define differentinitialization sequences in the subset 28-2 as a function of the singleparameter z (Block 300). Processing further includes generating theuplink reference signal 22-2 with the sequence generator initialized tothe derived initialization sequence 26-2 (Block 310), and transmittingthe generated signal 22-2 (Block 320).

In embodiments where the base station 12-1 has encoded the secondinitialization sequence 26-2 to be a single parameter z that comprises adefined number of least significant bits from the second sequence 26-2,the wireless device's derivation entails padding the single parameter zwith a defined number of zeroes. In some embodiments, this paddinginvolves appending the defined number of zeroes to the single parameterz. In other embodiments, though, padding includes pre-pending thedefined number of zeroes to the single parameter z. In this case, thedevice 16-2 effectively derives a second sequence 26-2 that has its mostsignificant bits padded with zeroes.

By contrast, in embodiments where the base station 12-1 has encoded thesecond initialization sequence 26-2 according to a defined one-to-onemapping with the single parameter z (e.g., as in FIG. 5), the device16-2 derives the sequence 26-2 based on that same mapping. In someembodiments, for example, the device 16-2 stores the look-up table ofFIG. 5 in memory and references that table to map the received parameterz to the second initialization sequence 26-2 c_(init). Such may entailconverting the decimal representation of c_(init) into a correspondingbinary representation. In other embodiments, the device 16-2 derives thesecond initialization sequence 26-2 c_(init) according to an algorithmor formula that is the counterpart to that used by the base station 12-1to encode the sequence 26-2. For example, the device 16-2 derives thesequence 26-2 c_(init) according to

$c_{init} = {z + {2{\lfloor \frac{z}{30} \rfloor.}}}$

In embodiments where the sequence 26-2 c_(init) corresponds to a CSHpattern, the device 16-2 generates the uplink reference signal 22-2 bydetermining the CSH pattern from the derived sequence 26-2. The device16-2 then applies the CSH pattern to a cyclic shift, and finally appliesthe resulting cyclic shift to a base sequence to generate the uplinkreference signal 22-2. Of course, where the single parameter z jointlyencodes the sequence 26-2 as well as CSH_ENABLE, the device 16-2 derivesCSH_ENABLE according to one or more rules that define CSH_ENABLE as afunction of the parameter z, and then selectively determine and apply aCSH pattern depending on CSH_ENABLE.

Although embodiments illustrated with respect to FIGS. 5-7 show thesecond sequence 26-2 encoded as a single parameter z, other embodimentsherein encode the second sequence 26-2 as a linear combination of twoparameters x, y; that is, instead of the second set 32-2 of parametersin FIG. 3 comprising only a single parameter z, the second set 32-2comprises two parameters x, y. In this case, parameter y encodes adefined number of least significant bits from the second sequence 26-2.Parameter x encodes a defined number of more significant bits from thesecond sequence 26-2, not including one or more most significant bitsfrom the second sequence 26-2, i.e., those defined number (e.g., 21) ofmost significant bits that are 0's. FIG. 8 illustrates an example ofthis where a look-up table embodies the linear combination of x, y.

As shown in FIG. 8, the look-up table maps the linear combination of x=0and y={0, 1, . . . 29} to possible initialization sequences c_(init)={0,1, . . . 29}. Similarly, the table maps the linear combination of x=1and y={0, 1, . . . 29} to possible initialization sequencesc_(init)={32, 33, . . . 61}, and so forth up. With the range of x being{0,16} and the range of y being {0,29}, the second sequence 26-2 isencoded with 10 bits, including 5 bits for x and 5 bits for y.

FIG. 8 of course illustrates the defined mapping as being a look-uptable that is obtained by the base station 12-1 for encoding. The basestation 12-1 in some embodiments obtains the table from memory, while inother embodiments the base station 12-1 obtains the table by generatingit on an as needed basis, according to a predefined formula. In eithercase, the base station 12-1 selects the second sequence 26-2 c_(init)from the second subset 28-2 and then determines the parameters x, y thatcorrespond to the selected sequence c_(init) in the look-up table. Thedevice 16-2 receives these parameters x, y and correspondingly derivesthe second sequence 26-2 according to this same mapping.

In other embodiments, the mapping is embodied in ways other than alook-up table. In one embodiment, for example, the defined mappingexists as an algorithm or formula used by the base station 12-1 forencoding and by the device 16-2 for decoding. Specifically, the basestation 12-1 encodes the selected initialization sequence c_(init) asthe parameters x, y, and the device 16-2 decodes the sequence c_(init)as a function of the parameters x, y, according to c_(init)=32x+y.

As briefly mentioned above, the base station 12-1 in some embodimentsinitializes the sequence generators for the different devices 16-1, 16-2with a common initialization sequence. Thus, in this case, the basestation 12-1 selects the first and second sequences 26-1, 26-2 so thatthey are the same. In some embodiments, the initialization sequenceselected is a common sequence because it is common among at least someof the devices 16 in the cell 14-1. For example, the initializationsequence selected, and the subsequent encoding thereof, depends on aphysical cell identity for the cell 14-1.

Where such embodiments employ LTE, for instance, the base station 12-1determines the decimal representation of the first and secondinitialization sequence 26-1, 26-2 according to

${c_{init} = {{\lfloor \frac{N_{ID}^{cell}}{30} \rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}},$

where N_(ID) ^(cell) is the physical cell identity for cell 14-1 andtakes on 504 different integer values, and f_(ss) ^(PUSCH) is thesequence-shift pattern for PUSCH that takes on 30 different integervalues {0,29}. Hence, it can be seen that the range for c_(init) is{0,541}. The base station 12-1 encodes the first initialization sequence26-1 for the first device 16-1 as a set 32-1 of parameters that simplyincludes N_(ID) ^(cell) and f_(ss) ^(PUSCH). Even though the secondinitialization sequence 26-2 for the second device 16-2 is the same asthe first sequence 26-1, the base station 12-1 encodes that secondsequence 26-2 differently, according to any of the embodiments describedabove. The base station 12-1 may for instance encode the second sequence26-2 as the single parameter z (either directly as the 10 leastsignificant digits of the sequence, or by mapping the sequence to theparameter z), or encode the second sequence 26-2 as the parameters x, y,where

$x = \lfloor \frac{N_{ID}^{cell}}{30} \rfloor$ andy = f_(ss)^(PUSCH).

In other embodiments, the base station 12-1 initializes the sequencegenerators for the different devices 16-1, 16-2 with different sequencesthat are device-specific. In this case, the base station 12-1 determinesthe initialization sequences 26-1, 26-2 based on at least one parameterthat is device-specific. In at least some embodiments, the base station12-1 determines the sequences 26-1, 26-2 without regard to the physicalcell identity.

In still other embodiments, the base station 12-1 initializes thesequence generator for the first device 16-1 with a cell-specificsequence, but initializes the sequence generator for the second device16-2 with a device-specific sequence. Where the embodiments employ LTE,for instance, the base station 12-1 encodes the first initializationsequence 26-1 for the first device 16-1 as a set 32-1 of parameters thatsimply includes N_(ID) ^(cell) and f_(ss) ^(PUSCH). By contrast, thebase station-12 determines the second initialization sequence 26-2 forthe second device 16-2 without regard to N_(ID) ^(cell) and then encodesthe second sequence 26-2 as the single parameter z, or encodes thesecond sequence 26-2 as the parameters x, y, where those parameters donot depend on N_(ID) ^(cell).

In at least some of these embodiments, the base station 12-1 initializesthe sequence generators in this way (i.e., in a cell-specific manner forthe first device 16-1 and in a device-specific manner for the seconddevice 16-2) in order to maintain backwards compatibility with respectto the first device 16-1, while achieving inter-cell orthogonality forthe second device 16-2 with respect to a third wireless device 16-3 in adifferent cell 14-2. Where the embodiments employ LTE, for example, thefirst device 16-1 comprises a legacy device that is configured for LTERel-8/9/10 and the second device 16-2 comprises a newer device that isconfigured for LTE Rel-11.

In some embodiments, the third device 16-3 is a legacy device. In thiscase, the base station 12-1 determines the second sequence 26-2 for thesecond device 16-2 by selecting from the second subset 28-2 theinitialization sequence that matches the initialization sequence for apseudo-random sequence generator of the third device 28-1. The basestation 12-1 is able to do this because the range of the second subset28-2 spans at least the range of the subset of possible initializationsequences for the third device 16-3; that is, the initializationsequence for the second device 16-1 is able to take on values that arepossible for the third device 16-3. With the initialization sequencesfor the second and third devices 16-2, 16-3 the same, the base station12-1 is able to achieve inter-cell orthogonality for these paireddevices 16-2, 16-3 through use of different orthogonal cover codes(OCCs) for the devices. Notably, therefore, by configuring theinitialization sequences in this way, the base station 12-1 is able toarbitrarily pair a newer device 16-2 in cell 14-1 with any legacy device16-3 in a different cell 14-2 for achieving inter-cell orthogonalitybetween those devices' uplink reference signals 22-2, 22-3.

In the above embodiment, the base station 12-1 may receive theinitialization sequence for the third device 16-3 from the base station12-2 serving cell 14-2. Alternatively, the base station 12-1 mayotherwise obtain that sequence, such as through knowledge of N_(ID)^(cell) for cell 14-2 in embodiments wherein the sequence for the thirddevice 16-3 is cell-specific. Of course, the base station 12-1 may paira newer device 16-1 in cell 14-1 with newer devices in a different cell14-2 in analogous manner.

Those skilled in the art will appreciate that while the aboveembodiments were illustrated with particular values, the embodiments arenot limited in this respect. For example, although the second set 32-2of parameters was described as being 9 or 10 bits, and the secondsequence 26-2 as being 31 bits, other bit sizes are possible. Likewise,while the ranges of the first and second subsets 28-1, 28-2 weredescribed as spanning between a minimum value of 0 and a maximum valueno greater than 541, other ranges are possible.

Furthermore, those skilled in the art will appreciate that althoughterminology from 3GPP LTE-Advanced has been used to describe embodimentsherein, this should not be seen as limiting the scope of the inventionto only the aforementioned system. Other wireless systems, includingWCDMA, WiMax, UMB and GSM, may also benefit from exploiting thetechniques herein.

Also note that terminology such as base station and wireless device(e.g., UE) should be considering non-limiting and does in particular notimply a certain hierarchical relation between the two; in general “basestation” could be considered as device 1 and “UE” device 2, and thesetwo devices communicate with each other over some radio channel.

Although the above embodiments focused on the UL of an LTE Rel-11network, other embodiments may be applied even to the DL and to othercommunication protocols.

In view of the above modifications and variations, those skilled in theart will appreciate that FIG. 9 illustrates an example wireless device16-2 configured according to one or more embodiments herein. As shown inFIG. 9, the wireless device 16-2 is at least logically divided into anapplication processor 46 that runs user-oriented functions (softwareapplications, user interface control, etc.) and an access processor 48that implements the air interface protocols, including any encryptionand authentication processing needed for network access and subscriberaccounting via transceiver circuits 42 and antenna(s) 40.

In general, the wireless device 16-2 includes one or more processingcircuits 44, such as microprocessors, digital signal processors, orother digital processors, and associated memory or othercomputer-readable media, for storing, e.g., a computer program theexecution of which configures the device 16-2 according to the teachingsherein. In particular, the device 16-2 includes a processing circuit(e.g., a reference signal generator) 46 that is specially configured,e.g., by the execution of stored computer program instructions, togenerate a reference signal for transmission as described above.

Specifically, the processing circuit 46 is configured to selectivelyderive one of the initialization sequences within a subset of possibleinitialization sequences for the sequence generator, according to one ormore rules that define different initialization sequences in the subsetas a function of a single parameter. The processing circuit 46 isfurther configured to generate the uplink reference signal based on thederived initialization sequence, and to transmit the generated signalvia the transceiver 42.

FIG. 10 likewise illustrates an example base station 12-1 configuredaccording to one or more embodiments herein. Those skilled in the artwill recognize that the base station 12-1 in one or more embodimentsincludes one or more processing circuits 56, such as microprocessors,digital signal processors, or other digital processors, and associatedmemory or other computer-readable media, for storing, e.g., a computerprogram the execution of which configures the base station 12-1 toperform the processing shown in FIG. 2 or 4

When configured to perform the processing shown in FIG. 2, the basestation 12-1 includes one or more processing circuits (e.g.,control/signaling circuits) 58 that are specially configured, e.g., bythe execution of stored computer program instructions, to initializepseudo-random sequence generators on which wireless devices 16 basegeneration of uplink reference signals 22 as described above. The one ormore processing circuits 58 are configured to determine a first sequence26-1 from a first subset 28-1 of possible initialization sequences for apseudo-random sequence generator of a first wireless device 16-1. Theone or more processing circuits 58 are further configured to determine asecond sequence 26-2 from a second subset 28-2 of possibleinitialization sequences for a pseudo-random sequence generator of asecond wireless device 16-2. The range of this second subset 28-2 spansat least the range of the first subset 28-1. Moreover, the one or moreprocessing circuits 58 are configured to encode the first sequence 26-1as a first set 32-1 of two or more parameters, and to encode the secondsequence 26-2 as a second set 32-2 of one or more parameters. Thissecond set 32-2 comprises fewer bits than the first set 32-1, andincludes at least one parameter not included in the first set 32-1.Finally, the one or more processing circuits 58 are configured toinitialize the sequence generators of the first and second devices 16-1,16-2 with the first and second sequences 26-1, 26-2 by transmitting thefirst and second sets 32-1, 32-2 of parameters to the first and seconddevices 16-1, 16-2.

When configured to perform the processing shown in FIG. 4, the basestation 12-1 includes one or more processing circuits (e.g.,control/signaling circuits) 58 that are specially configured, e.g., bythe execution of stored computer program instructions, to initialize apseudo-random sequence generator on which a wireless device 16-2 basesgeneration of an uplink reference signal. The one or more processingcircuits 58 are configured in this regard to determine a sequence 26-2from a subset 28-2 of possible initialization sequences for thepseudo-random sequence generator of the device 16-2. The one or moreprocessing circuits 58 are configured to then encode the determinedsequence 26-2 as a single parameter z. Different values for this singleparameter z represent different possible initialization sequences withinthe subset 28-2. Finally, the one or more processing circuits 58 areconfigured to initialize the pseudo-random sequence generator of thewireless device 16-2 with the determined sequence 26-2 by transmittingthe single parameter z to the wireless device 16-2.

Those skilled in the art will recognize that the present invention maybe carried out in other ways than those specifically set forth hereinwithout departing from essential characteristics of the invention. Theembodiments are thus to be considered in all respects as illustrativeand not restrictive, and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

What is claimed is:
 1. A method implemented by a base station forinitializing pseudo-random sequence generators on which wireless devicesbase generation of uplink reference signals, comprising: determining afirst sequence from a first subset of possible initialization sequencesfor a pseudo-random sequence generator of a first wireless device;determining a second sequence from a second subset of possibleinitialization sequences for a pseudo-random sequence generator of asecond wireless device, the range of the second subset spanning at leastthe range of the first subset; encoding the first sequence as a firstset of two or more parameters; encoding the second sequence as a secondset of one or more parameters, wherein the second set comprises fewerbits than the first set and includes at least one parameter not includedin the first set; and initializing the sequence generators of the firstand second devices with the first and second sequences by transmittingthe first and second sets of parameters to the first and second devices.2. The method of claim 1, wherein the second sequence is encoded as asingle parameter comprising the second set.
 3. The method of claim 2,wherein the first and second sequences each comprise a defined number ofbits corresponding to the range of a full set of possible initializationsequences, and wherein the single parameter comprises a defined numberof least significant bits from the second sequence, the defined numberof least significant bits corresponding to the range of the secondsubset.
 4. The method of claim 2, wherein the second sequence is encodedbased on a defined one-to-one mapping of possible initializationsequences within the second subset to possible values for the singleparameter, wherein the range of the single parameter is smaller than therange of the second subset.
 5. The method of claim 4, wherein the secondsequence c_(init) is encoded as a single parameter${z = {c_{init} - {2\lfloor \frac{c_{init}}{32} \rfloor}}},$wherein └x┘ denotes a floor function that rounds x to the nearestinteger less than or equal to x.
 6. The method of claim 1, wherein thesecond sequence is encoded as a linear combination of two parameterscomprising the second set, wherein a first one of the two parametersencodes a defined number of least significant bits from the secondsequence and a second one of the two parameters encodes a defined numberof more significant bits from the second sequence not including one ormore most significant bits from the second sequence.
 7. The method ofclaim 1, wherein the second set of parameters comprises 9 or 10 bits,and wherein the second sequence comprises 31 bits.
 8. The method ofclaim 1, wherein the ranges of the first and second subsets each spansbetween a minimum value of 0 and a maximum value no greater than
 541. 9.The method of claim 1, wherein the ranges of the first and secondsubsets are different, but correspond to the same number of bits. 10.The method of claim 1, wherein the first initialization sequencecomprises a cell-specific sequence and the second initializationsequence comprises a device-specific sequence.
 11. The method of claim1, wherein each sequence corresponds to a cyclic shift hopping pattern,wherein a wireless device generates an uplink reference signal byapplying a cyclic shift hopping pattern to a cyclic shift and byapplying the resulting cyclic shift to a base sequence.
 12. The methodof claim 11, wherein determining the second sequence comprises selectingfrom the second subset the possible initialization sequence that matchesan initialization sequence for a pseudo-random sequence generator of athird wireless device, wherein the third device is served by a differentcell than the second wireless device.
 13. The method of claim 11,wherein encoding the second sequence comprises jointly encoding thesecond sequence and an indication of whether or not cyclic shift hoppingis enabled for the second device as the second set of one or moreparameters.
 14. A base station configured to initialize pseudo-randomsequence generators on which wireless devices base generation of uplinkreference signals, comprising a transceiver circuit and one or moreprocessing circuits configured to: determine a first sequence from afirst subset of possible initialization sequences for a pseudo-randomsequence generator of a first wireless device; determine a secondsequence from a second subset of possible initialization sequences for apseudo-random sequence generator of a second wireless device, the rangeof the second subset spanning at least the range of the first subset;encode the first sequence as a first set of two or more parameters;encode the second sequence as a second set of one or more parameters,wherein the second set comprises fewer bits than the first set andincludes at least one parameter not included in the first set; andinitialize the sequence generators of the first and second devices withthe first and second sequences by transmitting the first and second setsof parameters to the first and second devices.
 15. The base station ofclaim 14, wherein the second sequence is encoded as a single parametercomprising the second set.
 16. The base station of claim 15, wherein thefirst and second sequences each comprise a defined number of bitscorresponding to the range of a full set of possible initializationsequences, and wherein the single parameter comprises a defined numberof least significant bits from the second sequence, the defined numberof least significant bits corresponding to the range of the secondsubset.
 17. The base station of claim 15, wherein the second sequence isencoded based on a defined one-to-one mapping of possible initializationsequences within the second subset to possible values for the singleparameter, wherein the range of the single parameter is smaller than therange of the second subset.
 18. The base station of claim 17, whereinthe second sequence c_(init) is encoded as a single parameter${z = {c_{init} - {2\lfloor \frac{c_{init}}{32} \rfloor}}},$wherein └x┘ denotes a floor function that rounds x to the nearestinteger less than or equal to x.
 19. The base station of claim 14,wherein the second sequence is encoded as a linear combination of twoparameters comprising the second set, wherein a first one of the twoparameters encodes a defined number of least significant bits from thesecond sequence and a second one of the two parameters encodes a definednumber of more significant bits from the second sequence not includingone or more most significant bits from the second sequence.
 20. The basestation of claim 14, wherein second set of parameters comprises 9 or 10bits, and wherein the second sequence comprises 31 bits.
 21. The basestation of claim 14, wherein the ranges of the first and second subsetseach spans between a minimum value of 0 and a maximum value no greaterthan
 541. 22. The base station of claim 14, wherein the ranges of thefirst and second subsets are different, but correspond to the samenumber of bits.
 23. The base station of claim 14, wherein the firstinitialization sequence comprises a cell-specific sequence and thesecond initialization sequence comprises a device-specific sequence. 24.The base station of claim 14, wherein each sequence corresponds to acyclic shift hopping pattern, wherein a wireless device generates anuplink reference signal by applying a cyclic shift hopping pattern to acyclic shift and by applying the resulting cyclic shift to a basesequence.
 25. The base station of claim 24, wherein the one or moreprocessing circuits are configured to determine the second sequence byselecting from the second subset the possible initialization sequencethat matches an initialization sequence for a pseudo-random sequencegenerator of a third wireless device, wherein the third device is servedby a different cell than the second wireless device.
 26. The basestation of claim 24, wherein the one or more processing circuits areconfigured to encode the second sequence by jointly encoding the secondsequence and an indication of whether or not cyclic shift hopping isenabled for the second device as the second set of one or moreparameters.
 27. A method implemented by a base station for initializinga pseudo-random sequence generator on which a wireless device basesgeneration of an uplink reference signal, comprising: determining asequence from a subset of possible initialization sequences for saidpseudo-random sequence generator; encoding the determined sequence as asingle parameter, wherein different values for the single parameterrepresent different possible initialization sequences within the subset;and initializing said pseudo-random sequence generator of the wirelessdevice with the determined sequence by transmitting the single parameterto the wireless device.